Marine vessels, and particularly small commercial or pleasure boats are often equipped with sensing devices which aid in the safety and navigation thereof. In many instances, the sensing devices utilize a transducer which is intended to be mounted on the exterior of the hull of the vessel. Such transducers may sense water temperature, speed of a vessel, depth of the water under the vessel, the presence of marine life in the water, etc. The transducers are connected to a readout device by means of a cable, which is able to carry electrical signals from the transducer to the readout. Some transducers and readouts may use a fibre-optic cable.
The most common technique for passing a cable through the hull of a small commercial or pleasure vessel is to simply drill a hole in the hull, pass the cable through the hull, provide some type of backing on either the inner or outer side of the hole, or both, and then fill the hole with a suitable marine-grade sealant. While this is certainly a simple technique, it does have many drawbacks, including the eventual failure of the seal as the sealant hardens over time, and then begins to decay.
One of the most common forms of transducers is that associated with a depth finder, and includes some type of a sonic send/receive unit, and frequently includes a speed-sensing device, which has a paddle wheel as part of the sensor. Common forms of this type of transducer is attached to a cable having a specific connector on the other end thereon, for meeting with a I/O device. For this type of a transducer and cable device, the hole that is formed in the vessel hull must be large enough to accommodate passage of either the transducer or the cable therethrough, as the devices are frequently intended to have a cable of a fixed length. The cable is not intended to have the connector or the transducer removed therefrom during installation. Such connectors generally have a diameter of between one-half and one inch, requiring a fairly large hole to be formed in the hull of the vessel. A hole of a size sufficient to allow passage of such a connector or transducer is not easily, permanently sealed with known through-hull plugs. Additionally, if it becomes necessary to remove the cable, the plug and sealant must be easily removed, without damage to the vessel or the cable. Known plugs require the sealant to be cut or drilled out of the hull, which may result in damage to the cable and enlargement of the bore. These are not desirable features.